Try these inputs in HR. It's an 18Hz TH I was messing with for the LMSR-15 early last year. This would not be a simple single angle, single fold but those almost always have a lackluster response unless you get very lucky. I would not consider building a TH with the poor response shown in the above sim. Look at the 2 octave 15-60Hz area below. (John try playing around with the inputs below in the wizard)

thanks ricci. i fat fingered entering the driver specs. can't remember the last time that i did that. anyways, myg, if nobody beats me to it, i'll try to throw together something that balances performance and ease of construction for your friend in the next day or so.

just a quick back of the envelope design. the numbers aren't precise, but the results won't change materially. this one has a constant expansion rate from throat to mouth, so would be a trivial build.

do you think that would work for your buddy? you can shift the whole show left and pick up a little more extension, by going larger. or, you can shift the whole thing to the right and pick up a little more spl. i'd probably nudge it a little to the left and put the low corner right on 20hz, but that will complicate the build. i'll explain that in a minute.

same frequency response, just as is and smushed. smushed is a technical term that means the image is rescaled to not look so choppy, as you will find most companies that make these things do.

here are some "napkin sketches" just to give you some idea of what we are talking about here. ignore the size difference.

the first is a single fold horn. the second is a little more involved, but is required if the total length of the first picture gets too long. they are both the same. the second one is the first one folded over onto itself.

ricci's design provides a flatter frequency response, but in a more complicated build. ah, tradeoffs.

i just happened to have hornresp set for 60 volts. that was arbitrary. the 1w1m response is very good at around 95db.

max spl varies by frequency but with a 2000 watt amp, per driver, 127db (1m 1/2 space) or so isn't out of the question. that is pretty damn loud. actually, that is too loud for anything but instanteous peaks.

So if I get this correctly, single folder means the cabinet will be very long ?

I will ask my friend about it today, but I actually don't think that will be a problem, because he has a huge space for the horns.. And if single folder is easier, then I guess it's a no brainer. But I will ask him!

ok. i'll provide a plan in the next day or so. since it has a constant expansion rate, it will be easy to design and build. ricci's has a little better frequency response, but like the gjallerhorn, the design and build get tricky.

two of these horns with proper power will have more than 130db from 20hz up. that is more than anybody needs (more than most anybody could take), so he should be happy. :-)

I can only assume something like 40 % movies / 60% music.... Decent output down to 17-18hz is probably more than enough. If it starts dropping at 20hz, he will still have quite the output down to 17-18hz at least?

i chose a width of 24" (61 cm). going with that, you are looking at a 5 x 6 foot enclosure (153 x 183 cm). are we heading in the right direction? this is a mockup. it is a monster, but when you want big bass without spending a ton of money, a monster is what you need,

You can cut about 200L or 25% off of that 775L behemoth and still get a little flatter response. You might lose maybe 3dB sensitivity which isn't too bad.Try tweaking the throat volume a little which will shrink the whole thing if using a single expansion just don't go below about 250cm the cone is strong enough to handle the pressures . Check your clearances for excursion with a 24" width too. You might even be able to put both 15's in one cab the size of this and get a decent response.

with respect to frequency response, i was thinking that +/- 1.5db (excluding the two notches) was "good enough". as you know, hornresp really makes things look choppy.

as for size, that is kind of an end user call. bigger is better, until it is too big for the user. his buddy gave the green light for an absolute monster 5x6x2 footer, but even i thought that was a little ridiculous. the current one is 4x5x2. still quite big, but the driver seems happy in it. do you think i should knock it down some more?

the compression ratio is just under 2.5:1.0. i don't want to push it more than that. on the off chance that a higher ratio would tear the driver apart, i would feel terrible and again the frequency response is pretty darn good as is.

This friend of mine is basically nuts, he is the guy who bought a new house in order to get better bass (That was the main reason hehe)... which he did.. But still not satisfied. So here comes the horn

Edit: Just talked to him, and the "smaller" one is better, simply because they sell the plywood in 220x120cm, which makes things a little easier.

Putting TWO LMS-R in one cabinet would be a good idea also, if there is much performance difference, he says.

Btw: When building a horn like this, I assume plywood will do? Thickness? 19mm (3/4") or 22mm? (4/5")... or does it have to be as thick as 1" ?

Correction. Solid and extensive bracing is a MUST. There is a reason that Danley and other horn sub designers put so much bracing in them. With all of that extra efficiency and output comes greatly increased forces inside of the cabinets. Then factor in that horn subs are LARGE which means big panels and you have a recipe for significant cabinet flex, resonances and noise.

new house for bass. that's awesome. :-)
3/4" (19mm) wood is fine. a little bracing would be good. i'll include some ways to take care of that.
the main question is are you (and friend) happy with the frequency response and the overall size of the enclosures in post 24?
i'll nudge the size down a hair for 120cm plywood. i didn't know what you guys have over there.
smushed (1w1m). two notches required.just to put it in perspective. that is the same sensitivity that you would get out of 6 lms-r drivers in a total of 42 cubic feet ported with a 20hz tune. hoffman was right. ;-)

I had to bold that last line there...

But it all sounds good... Get the cabinet to work well with the 220x120cm plywoods, and he is good to go (or well, he is good to go when the drawings for the monster are ready).

This sounds like a lot of fun... Might make one myself if it performs as good as it seem to do!